IMHO assigning searchable keywords to images is fundamental to modern image management.
Preferably those keywords are embedded in the image metadata (IPTC or XMP) and do not only reside in the program's database. This allows to easily migrate your photos to a different DAM program in the future (Digital Asset Management). A DB is also desirable to speed up sorting/searching/browsing operations of large collections.
Among the free programs,
Faststone or Irfanview do not allow to assign/embed keywords, while free XNView and cPicture can do it AND include a search tool (no DB though).
Picasa does everything that is needed; it has a great interface, has a DB, performs well and allows to easily tag/caption/search your pictures. Tags and pics get embedded into JPEG IPTC metadata. The latest 2.5 beta does show folder structure and can embed "Geotags" (long./lat.) into a picture´s EXIF data with the help of GoogleEarth:http://fileforum.bet...Windows/1067993856/1
Managing RAW files does get tricky as it is usually not possible to embed metadata into RAW files (and not recommended if possible). You either write it to an XMP sidecar file or else convert to Adobe DNG raw which is designed to have embedded metadata and preview.
Programs such as Idimager, IviewMediaPro and Imatch can write keywords to XMP/DNG; they are not free, IviewMP being the priciest (but has an academic discount).
Picasa 2.5 can read RAW files (incl DNG) but will not embed captions or tags into them; as a RAW user, my workaround is to shoot RAW+JPEG and to embed captions/tags into the JPEGs, which also act as very fast previews (if I have a JPEG I don´t need Picasa to show me the RAW file).
Incidentally those RAW shooters that convert to adobeRGB should be aware that Picasa is not colorprofile aware, use an external viewer that is (such as Faststone but not XNview or Irfanview).
I did try the latest ACDSee and although ACDSeePro has an IPTC editor I believe it will not embed keywords into IPTC. Someone correct me if I am wrong.
Those are my hopefully useful 2 cents...
Also, As it isand to successfully manage an image collection I think ii